Automatic return air piston and cylinder device



y 1955 E. P. SCHAFER 2,746,425

AUTOMATIC RETURN AIR PISTON AND CYLINDER DEVICE Filed Nov. 21, 1951 2Sheets-Sheet l ATTORNEY? y 1956 Y E. P. SCHAFER 2,746,425

AUTOMATIC RETURN AIR PISTON AND CYLINDER DEVICE Filed Nov. 21, 1951 2Sheets-Sheet 2 IN V EN TOR A TTORNEYS AUTOMATIC RETURN AIR PISTON ANDCYLINDER DEVICE Eugene P. Schafer, EastCleveiand, Ohio, assignor toGeneral Motors Corporation, Detroit, Mich, a corporation of DelawareApplication November 21, 1951, Serial No. 257,622 9 Claims. (Cl. 121-38)This invention relates to air cylinders and in particular to aircylinders of the type wherein the power stroke of the piston thereof isaccomplished upon the application of compressed air to the cylinder andthe return stroke of the piston is automatically responsivev to releaseof the compressed air applied to the cylinder.

The primary object of the invention is to provide improved, positiveacting air cylinders with automatic piston return responsive to therelease of accumulated compressed air applied thereto during the powerstroke of the piston thereof. i

A further object of the invention is to provide improved air cylinderswith automatic piston return ,wherein a portion of the air employed tomove the piston thereof on its power stroke is trapped within a plungerserving as an air accumulator movable with said piston, which entrappedaccumulated air returns the piston and plunger automatically responsiveto the release of air supplied to the cylinder during the power strokeof the piston.

Still another object of the invention is to provide improved and simplyconstructed valving and port means within automatic return air cylindersof the type embodying the invention.

7 Other objects of the invention will become apparent by reference tothe following detaileddescription taken in connection with theaccompanying drawings, in which:

.Fig. 1 is a longitudinal sectional view showing a typical installationof an automatic air return cylinder embodying the invention, a controlvalve therefor being shown diagrammatically.

Fig. 2 is a sectional view taken on the line 22 of Fig. 1. v

i Fig. 3 is an enlarged longitudinal sectional view of the automatic airreturn cylinder shown in Fig. 1.

Fig. 4 is a detailed sectional view taken on the line 4-4 of Fig. 3. i i

Fig. 5 is an enlarged longitudinal sectional view of another embodimentof the invention with the piston and plunger disposed in its normalposition before the application of air pressure to initiate the powerstroke.

Fig. 6 is a longitudinal sectional view similar to Fig. 5 showing thepiston and plunger at the end of the power stroke. i

Fig. 7 is a fragmentary longitudinal sectional view similar to Fig. 6showing the piston and plunger at the beginning of the return stroke.

Fig. 8 is a detailed sectional view taken on the line- 88 of Fig. 5. I 1

Referring now to the drawings where like numerals refer to like andcorresponding parts throughout the several views, the embodiment of theinvention disclosed in Figs. 1-4 inclusive is shown in application to adie as a Work kicker" for illustrative purposes only and without theintentionof so limiting the application or use of the invention, andcomprises in general a cylinder 10 having a piston 11 reciprocablymounted therein, a hollow piston rod 12 reciprocally extending throughone end of the cylhinder 10 connected to said piston forming anair-reset 10 whereupon the said compressed air from the piston rodPatented May 22, 1956 voir 13 within the said piston rod 12, the saidpiston 11 having a passage 14 axially therethrough from its head endcommunicating with the piston rod reservoir 13, and a valve elementshown in the form of a'ball valve 15 located in said piston 11 arrangedto open the passage 14 therethrough when compressed air enters thecylinder 10 through its single main port 16 to move the said piston 11on its power stroke simultaneously compressing air in the piston rodreservoir 13, the said valve element 15 closing and entrappingcompressed air in the piston rod reservoir 13 upon the exhaustof thecompressed air in the cylinder reservoir 13 then passes throughtheradial ports 17 in the piston 11. to behind the piston 11 to returnthe said piston 11 and piston rod 12 back to their normal position showninFig.1.. i

. At least a portion of the piston lli-s smaller in diameter than thebore of the cylinder 10 to provide an air passage 18 from the radialports 17 to the cylinder 10 behind the piston 11 which may be termed thereturn air chamber 19. The piston 11 is provided with a circumferentialring groove 26) preferably somewhat wider than the diameter of theO-ring seal 21 therearound whereby to permit compressed air entering thecylinder 10 through the main port 16 to get behind the said O -ring seal21 to seal more effectively the clearance provided between the piston 11and cylinder 10. Obviously, the O-ring 21 shifts in its ring groove 20to the opposite shoulder of the groove when compressed air from the airreservoir 13 in the piston rod 12 passes through the radial ports 17 tothe return air chamber 19.

The ball valve element 15 comprises a ball 26 seatable in its properoperating position' in the counterbore 22.

Theradial'ports 17 in the piston ll communicate with the ballcoun'te'rbore 22 in such a location as to permit compressed air from theair reservoir 13 in the piston rod 12 which is open to the ballcounterbore 22 to pass therethrough to the return air chamber 19 behindthe piston 11 when the ball 26 of the ball valve elementlS is seated,which seating occurs upon'the release of air pressure from the cylinder'10 ahead of the piston 11. The ball retainer ring 25 of the ball valve15 has an aperture 250 therethrough eccentric in respect to the ballcounterbore 22 which prevents the ball 26 of ,the ball valve 15 fromclosing communication between the air passage 14 in the piston 11 aroundthe ball 26 to the air reservoir 13 in the piston 11.

The head end of the cylinder 10 may be closed by any suitable means suchas an exteriorly threaded nut 28 having the main port 16 therethrough.The nut 28 may be interiorly threaded at 29 to accommodate a suitableair hose connection 30. The rod end of the piston 11 is preferably scaleb3) welding a sleeve 31 in spaced relationship to the interior thereofwhereby to telescopingly accommodate an O-ring retainer 32 which isassembled into the cylinder 10 in the position shown in Fig. 3 with anO-ring 33 disposed longitudinally between the inner end of the saidsleeve 31 and a shoulder on the O-ring retainer 32. I

One of many uses and an installation of the invention pistonro d- 12during the power stroke of the is shown in Figs. 1 and 2 forillustrative purposes. A

therein into which is disposed the" cylinder 10 of an automatic return'air cylinder embodying the invention. The

cylinder is clamped in the desired position in the groove 37 'by a clamp'38 and studs 39. The main *port 16 in the head of the cylinder'10' isoperatively connected to a source of compressed air or air-intake 40 andto .an air exhaust 41 Zthrough'an air hose 42 and 'a suitable valve'43.-

In the position of the automatic return air cylinder 10 shown in .Figs.'1 and '3, the intake 40 has been closed, the exhaust 41 has beenopened, and the piston 11 has been fully returned. B y moving the valveelement 4300i:

the valve 43 to open the intake and close the exhaust thereby causingcompressed air to enter the cylinder v10, the piston 11 moves to theright'as viewed in Fig. 3 until the annular shoulder 110 of the piston11 abuts the annular shoulder 320 of the O-ring retainer 32. During theapplicationof compressed air to the cylinder 10, compressed air alsoenters the air reservoir .13 of the hollow piston rod 12 through the airpassage 14, the ball valve counterbore '22 around the 'ball '26, andthrough the ball retainer ring 25.. The movement of the piston .11 totheright causes the piston rod 12 to lift or kick the work W oh. .the.die36 ready ffor manual or conveyo movement from the press.

As soon as the valve element 430 of the control valve 43 is moved toclose the intake 40 and open the exhaust 41, compressed air stored inthe air reservoir '13 of the piston rod 12 takes over and closes .theball valve 15, and, as soon as the ball valve 15 is closed, compressed,air from the air reservoir 13 passes through the ball retainer ring 25,the ballcounterbore 22, the radial ports 17, through the air passage 18around the piston 11 and to the return air chamber 19. Air underpressure in the return air chamber 19 acts on the piston 11 to re-' turnthe piston 11 which retracts the piston rod12.

Obviously, the invention maybe used for many other purposes andinstallations than that illustrated :above, particularly where a powerstroke from a piston -is required and a self-return -.of the piston isnecessary or desirable.

Referring now to Figs. 5-8 inclusive, another illustration of anautomatic air return cylinder embodying the invention is shown in detailand comprises a cylinder 50 having a bore .51 .therethrough counterboredat each end at 52 and 53 preferably with a curved shoulder 54 and 55,respectively, at the base .o fzthe said counterbores, a piston 56reciprocatingly mounted in the said cylinder Stl, a hollow piston rod.57 having' an air reservoir 58 therein secured to the said piston 56,-a threaded plug 59 on't'he head end of the said cylinder havinga-single main port 60 therein through which compressed air is supplied:to and exhausted from the said cylinder 50. A sleeve-61 at .the rod endof the cylinder 50 welded in sealed relationship thereto closes theendof the cylinder 50 and provides .a sleeve bearing for thereciprocation of the hollow piston rod 57. An O-ring retainer sleeve 62is assembled in the cylinder 50in the position .shown .in Figs. 5-7inclusive and .retainsan O-ring 63 longitudinally'between the inner .endof .the said sleeve 61 and a shoulder of the O-ring retainer 62. A valve.and by-pass meansis associated with the piston56 =and=counterbore 53 ashereinafter described.

The'head end .560 of :the gPiStQD 56 is smaller in diameter than thebody section 561 thereof to ,provide an annular air passage 64 .aroundthe said'head end 560 of the piston "56. The piston 56 is'providedwith-acircumierential ring. groove 65 preferably somewhat wider than thediameter of the Oring seal .66 therein whereby to permit compressed airentering :the cylinder through the main port 60 to seal more effectivelythe joint between the large end 561 of the piston 56 and the bore 51-ofthe cylinder 50.

By referring to 'Fig. 5,, it will be observed that compressed .airentering the'cylinder 50moves ;the piston .56 to the right as viewed in:Fig. 5., :and continues to do so throughout the entire power stroke ofthe-piston 56 un1il the large body section 5610f thepiston56arrives:sub-

stantially at its fully extended position as shown in Fig. 6.

low piston rod 57 fully extended to the right as viewed in Fig. 6,compressed air travels through the annular air passage 64, by the O-ring66, through the counterbore 53 of the cylinder 50, through radiallydisposed grooves 67 in the large body section 561 of the piston 56 andthrough radially disposed ports 68 in the hollow piston rod 57 to theair reservoir 58 thereof charging it with compressed arr. I

AS'SOOR as air pressure is' removed from the cylinder 50 and exhausttherefrom begins, the piston '56 immediately starts its return strokeresponsive to compressed air .from ihe reservoir 58 in the hollow piston.rod 57 entering the counterbore 53 of the cylinder 50 from the radiallydisposed ports 68 in the hollow piston rod 57 and the radially disposedgrooves 67 in the head end 560 of the piston 56 which moves the O-ring62 to the left as viewed in Fig. '7'sealing the annular air passage '64,"and, responsive to compressed air stored in the air reservoir 58- ofthe hdllowpis'ton rod-57, "the piston 56 and the rod 57 returns to-theirinitial retracted position as indicated in Fig. '5 ready -for anotherpower stroke.

Although but two embodiments of the invention have been disclosed in thedrawings and described in detail, it'is o'bv'i'ons'that many changes maybe made in the size, shape, arrangement, and detail of the severalelements of'the invention, all withoutdeparting from the spirit andscope thereof as defined by the appended claims.

7 I claim:

'1. An automatic return air cylinder'comprising a closed end cylinderhaving a bore therethrough and counterbores adjacent theends thereof,apiston havingthe head portion thereof smaller in diameter than theremainder thereof, the said piston having an O-ring groove therearoundlocated where 'the diameter thereof is changed, an O-ring in saidgroove, a ho'llow piston rod serving as a compressed air reservoirconnected to the large end of said piston and extending in reciprocatingsealed relation through one end'of said cylinder forming a return airchamber within said cylinder, the said compressed air reservoir .havingapertures therein located adjacent the said piston communicating withthe said return air chamber.

'2. An automatic return air cylinder as claimed in claim 1 wherein theend of the said counterbores in each end of said cylinder is oppositethe said O-ring groove in said piston when the piston is at the ends ofits stroke, and the shoulder at the end of the said counterbores iscurved.

"3. An automatic return air cylinder comprising "a cylinder having abore therethrough -with an inlet port at 'its'head end and a counterboreadjacent the other end,.a

piston slidahly mounted within said cylinder 'bore for reciprocatingmovement substantially throughout the length of said bore andcounterbore, ahollow piston rod serving as a compressed air reservoirconnected to the end of said piston remote from said port and extendingin reciprocating sealed relationship through the other end of saidcylinder, the annular space between the inner wall of said cylinder andat least a portion of said piston and rod assembly .form'inga return airchamber within said cylinder, said compressed air reservoir having anaperture therein communicating with said return air chamber, said pistonincluding a head portion-of smaller diameter than the remainder thereofin air flow communication with said .cylinderinlet, and valve meansmounted ture therein communicating with said return air cham' her, anannular groove located intermediate the ends of said piston, and a valvemember axially shiftably mounted within said groove in sealing slidingengagement with said bore to check air flow between said main port andsaid return air chamber until said intermediate portion of said pistonenters the counterbored portion of said cylinder.

5. An automatic return air cylinder comprising a closed cylinder havinga bore therethrough with a main port at its head end and a counterboreadjacent the other end, a piston slidable in said bore, a hollow pistonrod serving as a compressed air reservoir connected to the end of saidpiston remote from said port and extending in reciprocating sealedrelationship through the other end of said cylinder, the annular spacebetween the inner wall of said cylinder and at least a portion of saidpiston and rod assembly forming a return air chamber within saidcylinder, said compressed air reservoir having apertures thereincommunicating with said return air chamber, said piston having a headportion of smaller diameter than the remainder thereof, an annulargroove located between the different diameter portions of said piston,and an O-ring of predetermined diameter axially shiftably mounted withinsaid groove to sealingly slidingly engage said bore and provide a radialclearance with said counterbored cylinder portion to permit air flowbetween said main port and saidreturn air chamber as the ring enterssaid counterbored cylinder portion.

6. An automatic return air cylinder, as defined in claim 5, wherein theforward end of said counterbore is substantially opposite the O-ringgroove when the piston is at the end of its power stroke.-

7. An automatic return air cylinder unit comprising a cylinder having abore therethrough with an air supply port at one end and a counterboreat the opposite end, a piston having a head portion of smaller diameterthan said bore and a main body portion of smaller diameter than saidcounterbore, said piston being slidably mounted in said bore and formingwith the inner wall of said cylinder a working chamber in communicationwith said supply port, a hollow piston rod serving as a compressed airreservoir connected to the main body of said piston remote from saidport and extending in reciprocating sealed relationship throughsaidopposite end of the cylinder, the annular space between the inner wallof said cylinder and at least a portion of said piston and rod assemblyforming a return air chamber within said cylinder remote from said port,said compressed air reservoir having at least one aperture formedtherein maintaining air flow communication with said return air chamber,an annular groove between the head and main body portions of saidpiston, and an O-ring axially shiftably mounted within said groove insliding sealing engagement with the bore of said cylinder to precludeair flow between said working chamber and said air reservoir until saidintermediate portion of the piston enters said counterbored cylinderportion.

8. An automatic return air cylinder unit comprising a cylinder having abore therethrough with an air supply port at one'end and counterbore atthe opposite end, a pis-- ton having a head portion of smaller diameterthan said bore and forming therewith a first annular air passage andhaving a main body portion of smaller diameter than said counterbore andforming therewith a second annular air passage, said piston main bodybeing slidably mounted in said bore and the face of said piston headportion forming with the inner Wall of said cylinder a working chambercommunication with said port and said first air passage, a hollow pistonrod serving as a compressed air reservoir connected to, the main body ofsaid piston remote from said port and extending in reciprocating sealedrelationship through the opposite end of said cylinder, the annularspace between the inner wall of said cylinder and at least a portion ofsaid piston and rod assembly forming a return air chamber within saidcylinder remote from said port and adapted to communicate with saidsecond air passage, said compressed air reservoir having aperturestherein maintaining air flow communication with said return air chamber,an annular groove between the head and main body portions of saidpiston, and an O-ring axially shiftably mounted within said groove insliding sealing engagement with the bore of said cylinder to check airflow between said working chamber and said air reservoir through saidfirst and second passages.

9. An automatic return air cylinder comprising a cylindcr having a boretherethrough with an inlet port at its head end and a counterbore at theother end, a piston assembly received within said cylinder forreciprocating movement substantially throughout the length of saidcylinder bore and counterbore and including a piston and a hollow pistonrod extending in reciprocating sealed relationship through the other endof said cylinder, said piston and rod assembly with the inner wall ofsaid cylinder de fining an annular return air chamber within saidcylinder remote from said inlet port, said hollow piston rod including acompressed air reservoir therein having apertures communicating withsaid return air chamber, said piston being in sliding contact with saidbore and out of contact with said counterbore throughout a first portionof its length and including a second portion of smaller diameter thansaid bore terminating in a pressure face in communication with saidcylinder inlet, the first and second portions of said pistoncooperating, respectively, with the cylinder counterbore and bore toform an annular References Cited in the file of this patent UNITEDSTATES PATENTS (Addition to)

